Pressure sensitive transfer element



July 13, 1965 E. KRUMBEIN ETAL 3,194,676

' PRESSURE SENSITIVE TRANSFER ELEMENT Filed Dec. 6, 1961 United StatesPatent O 3,194,676 PRESSURE SENSHTIVE TRANSFER ELEMENT Edgar Krumbeinand Sigo Musehter, Hannover, Germany, assignors to Columbia Ribbon andCarbon Manufacturing Co., Inc., Glen Cove, NX.

' Filed Dec. 6, 1961, Ser. No. 157,453 v Claims priority, applicationGermany, Dec. 14, 1960, W 29,084; Mar. 16, 1961, W 29,659

Claims. (Cl. 117-361) This invention relatesto` carbon and duplicatingpaper having a colour-spendinglayer based on a synthetic plastic bindermaterial, and more particularly to the utilization of a combination of.incompatible or substantially incompatible synthetic plasticvbindermaterials forvmaking the coating substance for such carbon andduplicating papers.

One yof the most essential requirements imposed on a carbon paper thepreparation of which is based on wax,

as well as on synthetic materials consists in that the carbon papershould rather remain plane, and not curlwhen stored or during use. Thecarbon paper must be insensitive to possible variations of extraneousclimatic conditions such as the iniiuence of the temperature andatmospheric humidity.

Although there were not wanting proposals directed to. the solution ofthis difficult problem, none of the efforts to neutralize the-tendencytoward rolling or curling by applying a wax or a synthetic resin on the.back of the carbon paper have up to now led to a satisfactory result.

The presentinvention solves the problem by providing` a novelink-releasing coating on the front-side of the carbon paper foundationrather than by treating the back of the carbon paper foundation.v

Ink-releasing layers are known which are based upon individual resinousbinder materials such as vinyl chloridevinyl acetate-copolymers, ormixtures of resinousbinder materials used in a ratio such they theyremain compatible with eachother. The compatibility ofresinousmaterials` withone another is a conventionally recognizedproperty whereby the-resinsk have the ability of producing opticallyclear solid solutions .after they have been dissolved to gether in amutual solvent and after the solvent has been evaporated. l the resinousmaterials are incompatible or are used in such a ratio that theircompatibility is exceeded, then at least a portion of the-resinseparates from the remainder and forms a blush or smoky appearance andloss of optical clarity in the final solid solution.

The present invention relates to the discovery that the tendency ofcarbon papers to curl or roll may be unexpectedly'overcome by using asthe binder material a mixture of synthetic resins which are at leastpartially incompatible with each other. The microscopic examination ofthe mixture invisible by an unaided eye as far asfits structure isconcerned shows that after the evaporation ofthe solvent the lsyntheticmaterials within thecolourspending layer have a superiine heterogeneousvalveolar structure. The writing or printing colour matter is storedwithin said honeycomb-like structure and is delivered'during thewritingv procedure in proportioned quantities so that the representationof the lettering is absolutely uniform.

According to the invention, in addition to the heteroi geneity betweenthe hlm-forming material (the synthetic material) and the colour matterproper existing in all known carbon papers based onY syntheticmaterials, the present ink-releasing layers also' have 'a' Veryessential heterogeneity between the incompatible synthetic materialsjointly used as film-forming binder materials.

In this connection it has surprisingly beeny discovered that a carbonand duplicating paper the colour-spending materials and which in thefinished state has a'micro? 3,i94,676 Patented July V13, 1965 porousalveolar structure does not tend 'toward rolling. Such a carbon paperdoes not require any additional means for preventing itfromrolling,-therebyavoiding disagreeable electrostatic charge is eithereliminated or at leastreduced by far.. v

According to another embodiment of this invention carbon papers areprovided for use in modern registering processes byincluding thereinmagnetic pigment as the coloring matter. Itis known by presentexperience that it was impossible to squeeze the magnetic pigments theaverage size of the particles of which is about 05p. out of the knownmicroporous layers of synthetic materials. While heavy magnetizableferric oxides arel sufiiierntly tine as individual particles, when insolvents they tend toward coagulation and thus cannot be maintainedsuiiciently movable in the communicating micropor'es of the usual layersof synthetic material. Contrary, thereto, the utilization ofincompatible film-forming binder-materials according to the presentinvention leads to the lelimination of the coagulation and thus to anintense lettering `which hassuflicient marginal sharpness and asul'lcient quan-f tity of magnetizable particles.

A few examples with respectto the preparationof the hlm-forming materialaccordingv to the present invention are set forth hereunder.

Example I It has been found that an emulsion of equal parts ofa 20%Asolution of a vinyl chloride-vinyl acetate copolymer and a 20% solutionof `a polystyrene is quite advantageous.

1.1 parts ofretlexn blue colour, 4.5 p arts` of gas black, i l 1.9 partsof Milori blue colour, y i 0.2 part of disperser Z,

13.1 parts of castor oil,

5.6 parts of mineral oil,

Y 0.4 part of preservative are pulverivzed in a three roller millandintermixed within a stirring apparatus with l Y 36.7 partsrof a 20percent vinyl chloride-vinyl acetatei weights ofthe utilized nonlmixablesynthetic'materials to layer of which is prepared of suchincompatible'synthetic the ratio 1:1, the greater theelectric neutralityof thev layer. r'Hence it /followsthat inthe above example,V the optimumhas been achieved, 7

` Example 2 By adding small-parts only, ofy nitrocelluloseor Vcollodioncotton, respectively, to-vinyl copolymers, the writving properties of`the thus obtained paper will not be impaired. y f' yThe alreadydescribed -elfect takes place also in this case.

4.8 parts of gas black,

2.2 parts of Milori blue colour, 0.2 parts of disperser Z,

18.8 parts of castor oil, and 0.4 part of preservative are pulverized ina three roller mill and intermixed in a turbulent stirrer With Y 517.6parts of a 20 percent vinyl chloride-vinyl acetatecopolymer solution(Vino flex) and 22.0 parts of a 15 percent .solution of medium viscouscollodion cotton in a mixture of 95% 0f butanone and of methanol,

whereupon the raw paper is coated with this mixture in a manner knownper se.

Example 3 Only .at most of the entire content of the synthetic materialmay consist of cellulose ether, to be utilized with vinyl copolymers.

4.6 parts of gas black, 2.1 parts of Milori blue colour, 0.2 part ofdisperser Z,

18.4 parts of castor oil `and 0.4 part of preservative are pulverizedand intermixed inthe manner shown hereinabove with 60.5 parts of apercent vinyl chloride-vinylY acetatecopolymer solution (Vinollex) and13.8 parts of an ll percentsolution of medium viscous ethyl cellulose inmethyl ethyl ketone,

whereupon the raw paper is coated therewith in a manner known perse.

Example 4 The butadiene-styrene copolymers -are incompatable With vinylester copolymers in any ratio. In this case, too, thealready mentionedeffect is quite pronounced.

3.6 parts of gas black,

1.7 parts of Milori blue colour, 0.2 part of disperser Z,

14.2 parts of castor oil and 0.5 part of preservative are pulverized ina three roller mill and intermixed in a turbulent stirrer with 40.0parts of a 20 percent vinyl chloride-vinyl acetatecopolymer solution(Vinoflex) and 40.0 parts of a 20 percent solution of a copolymer ofbutadiene and styrene in methyl ethyl ketone.

The examples following hereunderV relate to -the preparation of a colourcomponent containing magnetic pigments.

Example 5 The colour component-consists of 12 parts magnetic ypigments S1l (the trade name of the Farbenfabriken a vinyl chloride-vinyl acetatecopolymer in methyl-ethyl trade name of Farbenfabriken Bayer,leverkusen).

ketone and 38 parts of a 20% polystyrene solution inmethyl-ethyl-ketone) to a permanent dispersion, Whereupon the mixture isapplied to a carrier material in a manner known per se. Y

The dehydrated castor oilin connection with a mineral oil can beyreplaced by blown castor oil `as a vehicle.

Example 6 The `colour component for a carbon paper based on syntheticmaterials according to the present invention canalso consist of amixtureof for example a PV-true blue B (BASF) andthe magnetic pigment S 1l (theIn this case, Y3.5 parts of the PV-true blue. (BASF) together with 5parts of castor oil, 4 parts of dehydratized castor oil and 3 parts `ofmineral oils (crystal oil) are pulverized at three intervals in athree-rollermill first, whereupon the space betweenV the rollers isincreased to 0.03 mm. and the aforesaid mixture intimately mixed on theroller with 5 parts of the magnetic pigment S ll. The thus obtainedpigment paste in stirred inthe turbulent stirrer together with 40 partsof a solution of the synthetic material according to the invention,namely a 20% solution of a vinyl chloride-vinyl acetate copolymer('Vinoflex) in methyl ethyl ketone and 39.5 parts of a 20% polystyrenesolution in methyl ethyl ketone to a permanent dispersion.

A llexible foundation is coated with this mixture in a manner known perse.

A sectional view of the carbon paper according to the present inventionin an enlarged scale is shown by way of example in the accompanyingdrawing;

The ink-releasing layer 2 ,consisting of a part 3 of synthetic bindermaterial'and of a part 4v of synthetic binder material is applied to aflexible foundation l which may be either a paper sheet or another foil.The part 3 of synthetic material is a non-coherent component of fineparticles between which there remains a free more or less largeintermediate space. The intermediate spaces are filled with the part ofsynthetic material of the other component of synthetic material whichforms a closed phase and thus produces the desired layer formation. Bothcomponents Vcontain capillary channels or pores 5 Which are filled withthe ink composition of the carbon paper. During the workingprocedure-that is, during writing, the ink composition of the carbonpaper isv squeezed out from the channels or pores 5.

What is claimed is: .Y

1. A pressure-sensitive transfer element comprising a flexiblefoundation having thereon a microporous inkreleasing layer comprising asthe solid binder material a mixture of synthetic plastic materials whichare incompatible Yin that they are incapable of forming an opticallyclear solid solutionafter being dissolved together in a mutual solventand after the solvent has been evaporated, said binder material havingdispersed therein a pressurereleas'able ink comprising oil and coloringmatter, the said "mixture of incompatible synthetic plastic materialscomprising lat least about 50% by weight of a vinyl resin .together witha sulicient incompatible amount by weight of a synthetic plasticmaterialV whereby the tendency of the ink-releasing-layer to Vcause thetransfer element to curl and roll is substantially completely avoided.

2. A-transfer element yaccording togclaim 1 `VinV which the mixture 'ofsynthetic plastic binder materials comprises a vinyl chloride-vinylacetate copolymer and polystyrene in a ratio 0fabout1:l. 5

3. A transfer element `according to claim l in which the mixture ofsynthetic plastic binder materials comprises a vinyl chloride-vinylacetate Lcopolymer and `a'butadiene copolymer. j j n v4. A transferVelement according tol claim 1 in which the mixture of syntheticplastic'binder materials comprises a -vinyl chloride-vinyl acetatecopolymer and a cellulose` ester plastic. l

5. A transfer element `according to claim 1 in which the syntheticplastic binder materials are present in a ratio of about 1:1.

6. A transfer element according to claim 1 in which the coloring mattercomprises magnetic pigment.

7. A pressure-sensitive transfer element comprising a ilexiblefoundation having thereon a microporous inkreleasing layer comprising asthe solid binder material a mixture of substantially incompatiblesynthetic plastic materials having dispersed therein apressure-releasable ink comprising oil and coloring matter, the saidmixture of incompatible synthetic plastic materials comprising lat leastabout 90% by weight of a vinyl resin together with up to about 10% byweight of a cellulose ether plastic whereby the tendency of theink-releasing layer to cause the transfer element to curl and roll issubstantially completely avoided.

S. A transfer element .according to claim 7 in which the cellulose ethercomprises ethyl cellulose.

9. A transfer element according to claim 7 vin which the vinyl resincomprises a vinyl chloride-vinyl acetate copolymer.

110. A transfer element according to claim 7 in which the coloringmatter comprises magnetic pigment.

References Cited by the Examiner UNITED STATES PATENTS 2,744,031 5/56Mumma 117-36.1 2,800,077 7/57 Marron l17-36.l 2,893,890 7/59 Harvey117-36.1 2,943,952 7/60 Clark 117-364 2,944,037 7/60 Clark 117-36.12,970,926 2/ 61 Findlay 1l7-36.1 2,984,582 5/61 Newman et al 117-3642,989,493 6/61 Clark et al. 117-16.1 3,029,157 4/62 Sutheim et al117-36.1 3,037,879 6/ 62 Newman et al 117-36.1

RICHARD D. NEVIUS, Primary Examiner.

20 MURRAY KATZ, WILLIAM D. MARTIN, Examiners.

1. A PRESSURE-SENSITIVE TRANSFER ELEMENT COMPRISING A FLEXIBLEFOUNDATION HAVING THEREON A MICROPOROUS INKRELEASING LAYER COMPRISING ASTHE SOLID BINDER MATERIAL A MIXTURE OF SYNTHETIC PLASTIC MATERIALS WHICHARE INCOMPATIBLE IN THAT THEY ARE INCAPABLE OF FORMING AN OPTICALLYCLEAR SOLID SOLUTION AFTER BEING DISSOLVED TOGETHER IN A MUTUAL SOLVENTAND AFTER THE SOLVENT HAS BEEN EVAPORATED, SAID BINDER MATERIAL HAVINGDISPERSED THEREIN A PRESURERELEASABLE INK COMPRISING OIL AND COLORINGMATTER, THE SAID MIXTURE OF INCOMPATIBLE SYNTHETIC PLASTIC MATERIALSCOMPRISING AT LEAST ABOUT 50% BY WIEGHT OF A VINYL RESIN TOGETHER WITH ASUFFICIENT INCOMPATIBLE AMOUNT BY WEIGHT OF A SYNTHETIC PLASTIC MATERIALWHEREBY THE TENDENCY OF THE INK-RELEASING LAYER TO CAUSE THE TRANSFERELEMENT TO CURL AND ROLL IS SUBSTANTIALLY COMPLETELY AVOIDED.